4:30 PM Sun February 17 2019

Doppler Radar appears to be showing the arrival of our wintry weather a little ahead of schedule.The Winter Weather Advisory is still in place for the northern counties of Maryland (north of Baltimore and southern PA). The icing will be light, but the earlier arrival might impact your Sunday evening plans. We should be thaw by Monday morning.

Update: See the NEW Winter Storm Watch Tue Night into Wed Night

Turning Colder As The Precipitation Arrives

Before showing the radar, I need to point out something first. The temperatures were just above freeing this afternoon, but the dew point was much lower. That is the level at which the moisture in the atmosphere would condense. When a storm arrives, the first round of precipitation can evaporate in the atmosphere. This cools the air the same way your skin feels chilly when you step out of the shower.

The evaporative cooling will allow the temps to drop a few degrees when the precipitation arrives. It can also allow rain to chance to sleet as it falls.

Temperatues

Dew Points

Compare the colder spots that are in the Winter Weather Advisory: Westminster and York have temps in the mid 30s, but Dew Points range from 18ºF to 20ºF. This will allow temps to drop below freezing when the sleet and freezing rain arrives.

Arriving A Little Sooner

Doppler Radar

Radar Simulation —> slider

The modeling has been slower and maybe underestimated what is arriving.
This slider looks less impressive than what is seen now.
We will need to nowcast this during the evening for intensity and road conditions

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Looking Ahead to Wednesday’s Storm

Most of our region wil see a burst of snow Wednesday morning as it arrives.
There will be enough for a few inches to fall before changing over.
More will fall in areas that will also get more icing along and west of I-95 into Southern PA.

Snow, Ice, Then Rain —> slider

While there will be a few inches of snow at the onset, it is too early to say how much before the mix and change over. The first indication of snow amounts will be tomorrow (within 48 hours of the event).
Plan for a change to rain around the Bay and south of The Bay Bridge during the afternoon and evening.
Ice will be a problem in same areas that had snow and ice last week.

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